Abstract: Aims The reed (Phragmites australis) is a long-rhizome clonal plant, widely distributed worldwide, with the plasticity and adaptability of changing the morphology and even growth form with changes in environment. The creeping ramet of reeds is a special growth form generated after the rhizome protrudes out of the alkali-spotted ground. This study aims to explore the growth patterns and the associated mechanisms of creeping ramets. Methods Statistical analysis was performed on the rhythm and pattern of super-growth and photosynthetic characteristics of creeping ramets. Additionally, the physiological integration among ramets was also studied. The methods used included the placement of hanging labels to regularly track ramet growth, measurement photosynthetic physiology of leaves at different leaf ages, and determination of 15N isotope levels. Important findings The results showed that in highly alkaline areas, reeds’ creeping ramets displayed different growth patterns compared to the contrast upward ramets. After 120 days of growth, the creeping ramets had an average length of (685.2 ± 118.75) cm, and their average growth rate during the observation period was (6.64 ± 3.51) cm?d–1. This was 15.4 times faster than the contrast ramets, indicating a logarithmic allometry growth pattern. The creeping ramets showed a rapid growth at first, followed by a slow down. On the other hand, the contrast ramets showed relatively stable linear isogonic growth process. The young leaves at the top of the creeping ramets had the same maximum photosynthetic capacity as the mature functional leaves. As the leaf order increases, the net photosynthetic rate of their leaves on the creeping ramets showed a logistic curve variation, while the contrast ramets showed a quadratic curve change that first increases and then decreases. Moreover, the theoretical maximum net photosynthetic rate of creeping ramets was 19.4% higher than that of the contrast ramets. The study found that creeping ramets treated with 15N isotopes had significantly higher levels of 15N abundance in various organs compared to untreated creeping ramets. Creeping ramets are a new adaptive feature of generalist species reed in extremely harsh alkali-spotted habitats. The super-growth of creeping ramets is attributed to the high photosynthetic rate of the top young leaves and the physiological integration process between tufted basal ramets and creeping ramets. This study provides new insights into the adaptation of reeds to extreme habitats. It also offers a research method for analyzing the super-growth of creeping ramets based on nutrient production and physiological integration, which has important theoretical significance.

Key words: clonal plant, physiological integration, 15N isotope, ramet growth form, assimilate transfer, extreme habitat, Plant ecology